Add error_code column to query insights documentation

Author: mstehrani

docs/relational-databases/system-views/queryinsights-exec-requests-history-transact-sql.md

@@ -53,6 +53,7 @@ The `queryinsights.exec_requests_history` in [!INCLUDE [fabric](../../includes/f
 | `data_scanned_memory_mb` | **decimal(18,3)** | Shows how much data was scanned from local memory. Data scanned from disk and memory together indicates how much data was read from cache. |
 | `data_scanned_disk_mb` | **decimal(18,3)** | Shows how much data was scanned/read from local disk. Data scanned from disk and memory together indicates how much data was read from cache. |
 | `command` | **varchar(max)** | Complete text of the executed query. |
+| `error_code` | **int** | Code of the first error encountered after query has begun execution. |
 
 ## Permissions